Trans-nozzle steam injection gas turbine

ABSTRACT

In a double-opposed flow gas turbine the fuel combustion chambers are arranged generally radially in a plane normal to the rotational axis of the turbine shaft. A generally annular turbine casing has an outer annular chamber of plenum distributing compressed air to the primary zones of the combustors and an inner annular chamber supplying steam to the secondary zones of the combustors which extend through the walls defining the air and steam chambers and supporting combined transition pieces and nozzles of the combustors as well as the turbine stator rings.

United States Patent Hugoson Apr. 25, 1972 [54] TRANS-NOZZLE STEAMINJECTION GAS TURBINE Birger O. Hugoson, Wallingford, Pa.

Westinghouse Electric Corporation, Pittsburg, Pa.

[22] Filed: Nov. 20, 1970 [21] Appl.No.: 91,301

Inventor:

[73] Assignee:

972,642 10/1910 Reed ..60/39.37 3,318,572 5/1967 Scalzo ..4l5/193FOREIGN PATENTS OR APPLICATIONS 283,290 1/1928 Great Britain ..60/39.55774,425 5/1957 Great Britain.. .....60/39.58 1,196,900 6/1961 Germany..60/39.59

Primary Iiraminer-Mark M. Newman Arr/slam litaminer-warrcn OlsenAttorney-A. T. Stratum. F. P. Lyle and F, Cristinno,.1r.

[5 7] ABSTRACT In a double-opposed flow gas turbine the fuel combustionchambers are arranged generally radially in a plane normal to therotational axis of the turbine shaft. A generally annular [56]References Cited I turbine casing has an outer annular chamber of plenumd15- UNITED STATES PATENTS tributing compressed air to the primary zonesof the combustors and an inner annular chamber supplying steam to the2,636,345 4/1953 Zoller ..60/39.55 Secondary Zones Ofthe combustorswhich extend through the 1,726,104 8/1929 Harr1s..... walls i g h i andsteam chambers and pp g 3,280,555 10/1966 Charpemler at m'60/3958combined transition pieces and nozzles of the combustors as 3,224,19512/1965 Walsh ....60/39.58 we asthe turbine Stator rings. 2,168,3138/1939 Bichowsky.... ....60/39.55 2,626,501 1/1953 Pavlecka et al..60/39.15 12 Claims, 5 Drawing Figures STEAM AIR I a I Q g] l 88 1 9 we38 5,

(f l) o o 4 ,74 71, i 76 7s 73 72 J Ma a PATENTEIJ APR 2 5 m2 SHEET 3 BF4 PATENTED APR 2 5 I972 SHEET 4 CF 4 FIG. 4

BACKGROUND OF THE INVENTION This invention relates, generally, toelastic fluid machines and, more particularly, to gas turbine powerplants of the open-cycle type.

As well known in the art, a gas turbine power plant type. of theopen-cycle type comprises an air compressor driven by a turbine forpressurizing air which is directed into combustion apparatus along withcombustible fuel for combustion, thereby providing hot pressurizedgaseous products of combustion to motivate the turbine. The powerdeveloped by the turbine in excess of that required to drive thecompressor is available to perform useful work.

Heretofore, in view of the metallurgical limitations of the combustionapparatus, the turbine components, and other elements in the regioninfluenced by the hot combustion products, only about 20 percent of thecompressed air has been utilized for combustion, and the remainder hasbeen utilized to reduce the temperature of the combustion products fromabout 3,500" F. to a temperature level that the above components cansafely withstand, about l,500 F. to 2,000 F. Thus, prior gas turbinepower plants have had a relatively high back work ratio and a relativelylow output work ratio.

Prior schemes have been proposed to reduce the back work ratio by theinjection of water or water and methanol mixtures into the aircompressor to cool the air during compression and thereby reduce theamount of compressor power required to compress the air to the properturbine inlet pressure. Although the above schemes are effective, thepercentage by weight of water that can be absorbed to humidify thecompressed air is relatively small, from 0.5 percent to about 2 percent,and the corresponding reduction in compressor power is likewiserelatively small.

Other schemes have heretofore been proposed for increas ing the coolingor quenching effect of the excess air delivered to the combustionapparatus by injecting vapor or vaporizable liquid, such as water orwater and methanol mixtures, into the combustion apparatus. Here again,the percentage by weight of liquid or vapor to the compressed air isrelatively small, from 0.5 to percent. Also, use of the foregoingschemes has been generally limited to periods of short duration, such asin aviation gas turbine engines where occasional bursts ofgreater powerare required.

Apparently, the use of the above-mentioned schemes has been limited forseveral reasons. First, with fluid injection the heat rate ofthe powerplant increased in proportion to the rate of liquid injection, therebyreducing the thermal efficiency of the power plant. Second, the cost andadded inconvenience of using liquid in the cycle of operation more thanoffset the greater power output capability of the powerplant within the5 water injection limit.

BRIEF SUMMARY OF THE INVENTION In accordance with one embodiment of thisinvention, the fuel combustion chambers for a double-opposed flow gasturbine are arranged generally radially in a plane normal to therotational axis of the turbine rotor shaft which extends through agenerally annular casing having an outer annular chamber or plenumdistributing compressed air to theprimary zones of the combustionchambers and an inner annular chamber distributing a vapor, such assteam, to the secondary zones of the combustion chambers which extendthrough generally cylindrical walls defining the air and the steamchambers and supporting combined transition pieces and nozzles of thecombustion chambers and also the turbine stator rings. The steam enterseach combustion chamber from the distribution chamber after firstflowing through a relatively narrow space between the combustor wall anda jacket surrounding each combustor, thereby imparting a relatively highvelocity to the steam to effectively cool the combustor wall. A steampressure higher than air pressure at the combustor may be utilized toimprove steam mixing. In the combined transition piece and nozzle foreach combustor the combustion products and steam mixture is acceleratedto a velocity and turned in a direction that will fit a free vortex flowpattern suitable for entry into the first stage rotor blade row. Aconsiderable part of the conversion to kinetic energy takes place afterthe gas mixture has left the nozzle throats. This provides theopportunity for additional mixing and mitigation of hot spots as well aspressure and velocity equalization thereby reducing blade excitationthroughout the turbine.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the:nature of the invention, reference may be had to the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIGS. 1A and 1B when combinedend-toend constitute a view, partly inlongitudinal section and partly in elevation, of a portion of a doubleflow gas turbine embodying principal features of the invention;

FIG. 2 is a quadrant view partly in elevation and partly in transversesection, taken generally along the line II--II in FIG. 1B;

FIG. 3 is a view, similar to a portion of FIG. 2, showing a modifiedarrangement for cooling the turbine rotor; and

FIG. 4 is a view, partly in section and partly in elevation, of themodified arrangement shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings,particularly to FIGS. 1 and 2, there is shown a portion of a gas turbine10 which is of the central admission, double-opposed flow type. Theturbine 10 comprises a generally annular casing 12 having a shaft 14extending through the casing and rotatably mounted in suitable bearingsdisposed in a bearing housing 16. In accordance with the usual practice,a compressor (not shown) may be connected to one end of the shaft 14 anda power generator (not shown) may be connected to the other end of theshaft. The shaft 14 is driven by a turbine rotor 1.8 described morefully hereinafter.

A generally annular exhaust housing 20 is attached to the left-hand endof the turbine casing 12 by means of an annular row of bolts 21. Asimilar exhaust housing, only a portion of which is shown, is attachedto the right-hand end of the casing 12 by bolts 21. The exhaust housing20 comprises an outer wall 22'and an inner wall 24 spaced from the wall22 to provide a generally annular exhaust passageway 26. An exhaust hood28, of any suitable type, is attached to the exhaust housing 20. Theproducts of combustion may be exhausted from the hood 28 to atmospherein the usual manner. A circular array of vanes 30 may be provided in theexhaust hood 28 to turn the stream of exhaust gas in radially outwarddirection.

As described in US. Pat. No. 3,3l8,572, issued May 9, 1967 to A..I.Scalzo and assigned to the same assignee as this application, thebearing housing 16 is supported in concentric relation with the innerwall 24 of the exhaust housing 20 by means of an annular array oftangential strut members 32. Likewise, the inner wall 24 is supported bythe outer wall 22 and an annular array of tangential strut members 34 isprovided for this purpose. Since the manner of operation of these strutmembers is fully described inissued patents; it will not be described inthis application.

As shown, the turbine rotor 18 is of the stacked type, and comprises aplurality of rotor wheels or discs 36 mounted on the shaft 14 andsecured together by an annular array of bolts 38 extending through thediscs 36 and end members 40. Each disc 36 carries an annular array ofrotor blades 42 of the usual type. The rotor 18 is of the multi-stagetype, with annular rows of stator vanes 44 disposed between annular rowsof rotor blades 42. The stator vanes 44 are supported by stator rings46. Energy for drivingthe rotor 18 is extracted from the motive fluid asit flows through the rotor blades in a manner well known in the art.

As explained hereinbefore, the present turbine is of the double-flowtype. Thus, two first stage rows of rotor blades 42 are axially apacedon the shaft 14 by a spacing member 48 to provide an annular space 50around the shaft 14. As shown by the arrows L and R in FIG. 1B, themotive fluid flows in opposite directions into the rotor blades 42 fromthe annular space 50.

In order to supply the motive fluid to the turbine, a plurality ofcombustion chambers or combustors 52 are arranged generally radially ina plane normal to the rotational axis of the shaft 14. The combustionchambers 52 are all substantially identical and of the canister type,each chamber having a primary zone 54 at its outer end, a combinedtransition piece and outlet nozzle 56 at its inner end and a secondaryzone 58 between the primary zone and the transition piece. The nozzle 56of each combustion chamber communicates with the annular space 50 aroundthe shaft 14 between the opposed first stage rotor blades 42 to supplythe motive fluid to the turbine rotor.

As explained hereinbefore, it is necessary to reduce the temperature ofthe combustion products in the combustion chambers to a temperaturelevel that the components of the turbine structure can safely withstand.Heretofore, this has been typically accomplished by utilizing a largeproportion of the compressed air from the compressor driven by theturbine to dilute and thus reduce the temperature of the combustionproducts. Therefore, prior gas turbine power plants have had arelatively high back work ratio and a relatively low output work ratio.In order to increase the output work ratio and decrease the back workratio of the present turbine, provision is made for quenching or coolingthe products of combustion by introducing a vapor, such as steam, intothe secondary zone 58 of each combustion chamber.

As shown, the turbine casing 12 has a generally annular outer chamber 60surrounding a generally annular inner chamber 62. The outer chamber 60is defined by an outer wall 64 of the casing and a generally cylindricalwall 66 which separates the inner and outer chambers. The inner chamber62 is defined by the wall 66 and a generally cylindrical wall 68. Thecombustion chambers 52 extend generally radially through said walls andare supported by a first cylindrical wall 66 and a second cylindricalwall 68. The turbine stator rings 46 are also supported by the wall 68.Each ring 46 has an annular projection 70 disposed in a groove 72 in asupporting ring 74 secured between offset portions 71 and 73 of the wall68. The transition piece 56 of each combustion chamber is supported by acollar 76 disposed in a groove 78 in the portion 73 of the wall 68. Asealing member 80 is provided around the opening in the wall 68 throughwhich the combustion chamber 52 extends.

A separate dome-shaped cap 82 is provided for each combustion chamber52. The cap 82 is attached to a supporting ring 84 secured in the outerwall 64 of the casing, as by welding. The cap 82, as best shown in FIG.1B, is attached to the ring 84 by bolts 86. Each combustion chamber 52is generally circular in cross section and extends through an associatedopening 88 in the ring 84 which is of a greater diameter than thediameter of the combustion chamber.

Likewise, the combustion chambers 52 extend through an associatedopening 90 in the wall 66 which is of a greater diameter than thediameter of the combustion chamber. A frusto-conical jacket 92 surroundseach combustion chamber 52 within the outer chamber 60. The base of thejacket 92 is secured to the wall 66 and the top of the jacket is sealedaround the combustion chamber. The volume of the space 94 between thejacket 92 and the combustion chamber is small relative to the volume ofthe combustion chamber for a purpose explained hereinafter. The insidesurface of the cap 82 may be lined with insulation 96 for heatprotection.

During operation of the turbine as viewed in FIG. 1B, compressed airfrom the compressor is admitted into the outer chamber 60 through aplurality of inlets 98, only plug of which is shown. Likewise, a vapor,such as steam, is admitted to the inner chamber 62 through a pluralityof inlets 100. The steam may be supplied from a steam generator or othersuitable source. A combustible fuel is admitted into the primary zone 54of each combustion chamber through a fuel injection nozzle 102 attachedto the cap 82. The compressed air enters the primary zone 54 through aplurality of perforations 104 in the wall of the combustion chamber toform a combustible mixture which is ignited by any suitable ignitionmeans such as a spark dug (not shown), to form hot gaseous products ofcombustion. The steam enters the secondary zone 58 of the combustionchamber through a plurality of perforations 106 after having passedthrough the relatively narrow space 94 between the jacket 92 and thewall of the combustion chamber, thereby increasing the velocity of thesteam. A rather high velocity is desired here to effectively cool thecombustor wall.

Furthermore, a steam pressure significantly higher than air pressure atthe combustor may be utilized to improve steam mixing. In this mannerthe steam is mixed with the combustion products in the secondary zone ofthe combustor.

Thus, the combustion products are diluted and cooled without interferingwith the combustion process in the primary zone of the combustor.

In the combined transition piece and nozzle 56 the combustion productsand steam mixture is accelerated to a velocity and turned in a directionthat will fit a free vortex flow pattern suitable for entry to the firststage rotor blade rows. A considerable part of the conversion to kineticenergy takes place after the gas and steam mixture has left the nozzlethroats 108, see FIG. 2. This provides the opportunity for additionalinter-mixing and mitigation of hot spots as well as pressure andvelocity equalization, thereby reducing blade excitation throughout theturbine.

As shown more clearly in FIG. 2, an annular row of stationary vanes 1 10may be provided between the throats 108 of the nozzles and the annularspace 50 around the shaft of the turbine. These vanes assist intangentially directing the motive fluid into the annular space 50 fromwhich it flows in opposite directions through the rotor blades 42.

In the modification of the invention shown in FIGS. 3 and 4, provisionis made for conducting vapor from the inner chamber 62 directly to thespace 50 around the shaft 14 close to the hub to reduce the temperatureat the center part of the rotor and also improve the temperature profilefor the blading. As shown, this may be done by means of tubes 112disposed between the nozzles 56 and supported by the collars 76 whichsupport the nozzles. The tubes 112 extend from the chamber 62 into theannular space 50.

From the foregoing description it is apparent that the inventionprovides a gas turbine structure having numerous advantages over priorstructures. Among these advantages are:

1. Cost reduction by elimination of the conventional first stage stator.

2. Ability to easily cool the combined transition piece and nozzle.

3. Reduction of hot spots on first stage stator vanes.

4. Reduces corrosion sensitivity of the turbine which normally isconcentrated at the first stage stator vanes.

5. Simplifies seal problem between combustor and transition piece.

6. Eliminates seal problem between conventional transition and firststage stator.

In addition to the foregoing, thermal expansion movements of thetrans-nozzle are not critical, since seals are only between stationaryparts. The structural stability and integrity of the turbine casing areinsured by symmetry and protection from heat. The cap arrangement offersa cost reduction by reducing the size of the turbine casing as well asimproving its strength. The overall size reduction achieved with thepresent arrangement permits unitized construction which need not bedismantled for shipment in conventional present power output ratings.

I claim as my invention:

1. A double-opposed flow gas turbine, comprising a generally annularcasing having an outer annular chamber surrounding an inner annularchamber,

a rotor shaft extending through said casing and having axially spacedrows of first rotor blades providing an annular space around the shaft,

a plurality of combustion chambers arranged generally radially in aplane normal to the rotational axis ofthe shaft, each combustion chamberhaving a primary zone at its radially outer end and a combinedtransition piece and nozzle at its radially inner end and a secondaryzone between the primary zone and the transition piece,

said nozzles communicating with the space around the shaft between thefirst stage rotor blades,

means admitting compressed air into the outer chamber for distributionunder pressure to the primary zones of the combustion chambers,

means admitting a vapor into the inner chamber for distribution to thesecondary zones of the combustion chambers, and

means admitting a combustible fuel into the primary zone of eachcombustion chamber.

2. The gas turbine defined in claim 1, wherein the vapor is steam.

3. The gas turbine defined in claim 1, wherein the casing includes anouter wall defining the outside boundary of the outer chamber, a firstgenerally cylindrical wall separating the inner and outer chambers, anda second generally cylindrical wall defining the inside boundary of theinner chamber.

4. The gas turbine defined in claim 3, wherein the combustion chambersextend generally radially through said walls and are supported by saidfirst and second walls.

5. The gas turbine defined in claim 3, including turbine stator ringssupported by said second wall.

6. The gas turbine defined in claim 4., including a separate cap foreach combustion chamber attached to the outer wall of the casing.

7. The gas turbine defined in claim 6, including insulation on theinside of each cap.

9. The gas turbine defined in claim 8, wherein the jacket is of afrusto-conical shape with its base attached to said first wall and itstop attached to the combustion chamber.

10. The gas turbine defined in claim 9, wherein the volume of the spacebetween the jacket and the combustion chamber is small relative to thevolume of the combustion chamber.

11. The gas turbine defined in claim 1, including means for conductingvapor from the inner chamber directly into the space between the rows offirst stage rotor blades.

12. The gas turbine defined in claim 11, wherein the vapor conductingmeans includes tubes disposed between the nozzles of the combinedtransition pieces and nozzles.

1. A double-opposed flow gas turbine, comprising a generally annularcasing having an outer annular chamber surrounding an inner annularchamber, a rotor shaft extending through said casing and having axiallyspaced rows of first rotor blades providing an annular space around theshaft, a plurality of combustion chambers arranged generally radially ina plane normal to the rotational axis of the shaft, each combustionchamber having a primary zone at its radially outer end and a combinedtransition piece and nozzle at its radially inner end and a secondaryzone between the primary zone and the transition piece, said nozzlescommunicating with the space around the shaft between the first stagerotor blades, means admitting compressed air into the outer chamber fordistribution under pressure to the primary zones of the combustionchambers, means admitting a vapor into the inner chamber fordistribution to the secondary zones of the combustion chambers, andmeans admitting a combustible fuel into the primary zone of eachcombustion chamber.
 2. The gas turbine defined in claim 1, wherein thevapor is steam.
 3. The gas turbine defined in claim 1, wherein thecasing includes an outer wall defining the outside boundary of the outerchamber, a first generally cylindrical wall separating the inner andouter chambers, and a second generally cylindrical wall defining theinside boundary of the inner chamber.
 4. The gas turbine defined inclaim 3, wherein the combustion chambers extend generally radiallythrough said walls and are supported by said first and second walls. 5.The gas turbine defined in claim 3, including turbine stator ringssupported by said second wall.
 6. The gas turbine defined in claim 4,including a separate cap for each combustion chamber attached to theouter wall of the casing.
 7. The gas turbine defined in claim 6,including insulation on the inside of each cap.
 8. The gas turbinedefined in claim 4, wherein each combustion chamber is generallycircular in cross section, said first wall has an opening therein foreach combustion chamber of a greater diameter than the diameter of thechamber, and including a jacket surrounding each combustion chamberwithin said outer chamber to direct Vapor from the inner chamber to thesecondary zone of the combustion chamber.
 9. The gas turbine defined inclaim 8, wherein the jacket is of a frusto-conical shape with its baseattached to said first wall and its top attached to the combustionchamber.
 10. The gas turbine defined in claim 9, wherein the volume ofthe space between the jacket and the combustion chamber is smallrelative to the volume of the combustion chamber.
 11. The gas turbinedefined in claim 1, including means for conducting vapor from the innerchamber directly into the space between the rows of first stage rotorblades.
 12. The gas turbine defined in claim 11, wherein the vaporconducting means includes tubes disposed between the nozzles of thecombined transition pieces and nozzles.